In certain industries, such as the automotive industry, it is conventional to move workpieces on a powered conveyor from station to station so as to permit sequential manufacturing operations to be carried out. The workpiece is typically mounted on a support pallet, and the pallet is moved from station to station by a powered conveyor. Such powered conveyor typically employs driven support rolls which support and drive the pallet from station to station. These conveyor rolls are continuously driven, and the pallet is typically stopped at the selected station by some type of stop device. This stop device is then required to stationarily and accurately hold the pallet at the selected workstation to permit the desired manufacturing and/or assembling operation to be carried out, or permit a precision-pallet locating device to engage the pallet, while at the same time the powered rolls continue to try to drive the pallet forwardly.
The conventional stop devices which are often employed involve a combination of heavy-duty springs and a solid (i.e. mechanical) stop. With such devices, however, the impact forces imposed on the stop, and also on the pallet, are often times excessive. Further, if heavy springs are utilized in an attempt to cushion the stoppage of the pallet, then these springs tend to urge the stopped pallet backwardly away from the stop, and such is obviously undesirable, and thus an anti-backup latch device is often required.
In an attempt to provide more successful cushioning of the pallet during stoppage thereof, some devices utilized air springs. Such attempts have met with only limited success in view of the limited force-absorbing character of such devices. Such devices also typically require anti-backup latch devices and/or sophisticated control systems to control air exhaust to prevent bounce back.
Other attempts to provide proper cushioning of the pallet have involved use of hydraulic shocks or cylinders. Examples of such devices are illustrated by U.S. Pat. No. 4,703,843 issued to Dixon, and U.S. Pat. No. 3,696,756 issued to Elmore et al. The Dixon device, however, involves both a complicated structure and a complex movement pattern, particularly a multiple-position movement pattern for the stop including both a stopping position and a fixturing position, whereby this device does not possess the desired degree of structural and operational simplicity. The Elmore et al device positions a hydraulic dashpot directly for contact with the moving load, and hence this device requires a support mechanism which permits the entire dashpot to be moved into and out of a position of contact with the load, thereby requiring undesired structural and functional complexities. Further, neither Dixon nor Elmore et al utilize hydraulic shock absorbers which are capable of providing proper stopping force over the stoppage distance, particularly as the load approaches the solid stop, so as to provide for more controlled and cushioned stoppage of the workpiece to minimize the impact against the solid stop.
Accordingly, it is an object of this invention to provide an improved cushioned stopping device suitable for stopping a moving load as associated with a continuously powered conveyor, which stopping device incorporates a hydraulic shock absorber which can provide for more controlled and cushioned stoppage of a moving load.
It is a further object of the present invention to provide an improved stopping device, as aforesaid, which minimizes the structural and functional complexities of the device and in particular simplifies the required movement of the elements thereof, which provides simple and reliable operation, and is economical for manufacture and assembly.
It is still a further object of the invention to provide an improved stopping device, as aforesaid, which can be mounted on a powered conveyor in such manner as to permit utilization of continuous through shafts extending sidewardly between opposite side rolls of the conveyor, rather than requiring use of stub shafts as is typical with many prior art structures, with the improved stopping device being mountable on the conveyor below the through shafts and having a stopping structure which can be positioned to project upwardly between the shafts to permit successful engagement and stoppage of the moving load, with the device employing a hydraulic shock absorber which is positioned downwardly below the through shafts.
Other objects and purposes of the invention will be apparent to persons familiar with structures and devices of this general type upon reading the following specification and inspecting the accompanying drawings.